1. Field of the Invention
The present invention relates to a video processing system, and more particularly, to a 2-dimensional non-linear interpolation system based on edge information and a 2-dimensional mixing interpolation system using the same.
2. Description of the Related Art
Generally, interpolation is used to perform a zooming function for magnifying or reducing a video signal. Video signals may include a signal having only a natural image or a signal in which text or graphics is mixed with a natural image. In the case of television sets, most video signals displayed have only natural images. On the other hand, computer monitors frequently output video signals in which text, graphics and natural images are mixed. For the magnification of complex video including text or graphics and a natural image to have a suitable output aspect ratio, it is essential for the interpolation to maintain the resolution of edges at portions such as graphics at which edge information is important, even after the interpolation.
However, many of the currently used interpolation methods are based on linear interpolation between pixels. These methods are advantageous in that noise decreases in natural image regions, but disadvantageous in that edge information cannot be effectively represented in graphic regions, when a video is magnified. Since edges are not specially considered in the linear interpolation, aliasing may occur at the edges. Consequently, edges are not represented clearly.
When magnifying an image using conventional 2-dimensional linear interpolation, smooth video without noise can be reproduced in natural image regions due to a smoothing effect. However, degradation in which edges become dull occurs in graphic image regions due to loss of high frequency components.
To address the above limitations, it is a first object of the present invention to provide a 2-dimensional non-linear interpolation system based on edge information, for clearly representing edges using 2-dimensional non-linear interpolation when a video signal is magnified.
It is a second object of the present invention to provide a interpolation method performed by the 2-dimensional non-linear interpolation system.
It is a third object of the present invention to provide a 2-dimensional mixing interpolation system for preventing the edge of a graphic image from being degraded when a video signal including both a natural image and a graphic image is magnified.
It is a fourth object of the present invention to provide a mixing interpolation method performed by the 2-dimensional mixing interpolation system.
In this manner, a new interpolation method is provided for reproducing smooth video images without noise due to a smoothing effect through interpolation, while preventing degradation of edges in graphic image regions.
Accordingly, to achieve the first object of the invention, there is provided a 2-dimensional non-linear interpolation system based on edge information. The system includes an edge detector, an edge direction modifier, a near-edge coefficient generator, a filter coefficient generator and a non-linear interpolation unit. The edge detector detects edge information among pixels from a video signal applied through an input terminal. The edge direction modifier converts the edge information detected by the edge detector on the basis of a center point among peripheral pixels of an interpolation position and outputs modified edge information. The near-edge coefficient generator converts the coordinates of the interpolation position based on the modified edge information to generate a converted interpolation position, generates edge patterns corresponding to the converted interpolation position, and generates a plurality of 2-dimensional interpolation coefficients in response to predetermined 1-dimensional non-linear interpolation filter coefficients. The filter coefficient generator generates the 1-dimensional non-linear interpolation filter coefficients in response to the coordinates of the converted interpolation position, the edge patterns and predetermined 1-dimensional filter coefficients. The non-linear interpolation unit multiplies data values associated with the peripheral pixels by the plurality of 2-dimensional non-linear interpolation coefficients to perform non-linear interpolation.
To achieve the second object of the invention, there is provided a method of performing 2-dimensional non-linear interpolation on an input video signal. The method includes steps (a) through (d). In step (a), edge information is detected from the input video signal. In step (b), the detected edge information is modified to generate modified edge information. In step (c), 2-dimensional non-linear interpolation coefficients are generated in response to the modified edge information and predetermined 1-dimensional non-linear interpolation filter coefficients. In step (d), data values associated with peripheral pixels around a current interpolation position are multiplied by the 2-dimensional non-linear interpolation coefficients, thereby performing non-linear interpolation on the video signal.
To achieve the third object of the invention, there is provided a 2-dimensional mixing interpolation system including an edge detection and non-linear interpolation coefficient generation unit, a linear interpolation unit, a non-linear interpolation unit and a multiplexer. The edge detection and non-linear interpolation coefficient generation unit detects edge information among pixels from a video signal input through an input terminal, modifies the detected edge information according to predetermined edge patterns, obtains a plurality of 2-dimensional non-linear interpolation coefficients based on the modified edge information among a plurality of adjacent pixels around a pixel to be interpolated, and generates an edge signal indicating the absence or existence of an edge among the plurality of adjacent pixels around the pixel to be interpolated. The linear interpolation unit multiplies data values associated with n*n pixels around the pixel to be interpolated by vertical interpolation coefficients and by horizontal interpolation coefficients to perform linear interpolation. The non-linear interpolation unit multiplies data values associated with the plurality of adjacent pixels by the plurality of 2-dimensional non-linear interpolation coefficients to perform non-linear interpolation near an edge. The multiplexer selectively outputs an interpolated pixel from the linear interpolation unit or an interpolated pixel from the non-linear interpolation unit in response to the edge information.
To achieve the fourth object of the invention, there is provided a method of performing 2-dimensional mixing interpolation on an input video signal. The method includes steps (a) through (e). In step (a), edge information among a plurality of adjacent pixels around a pixel to be interpolated is detected from the input video signal, and the detected edge information is modified into a predetermined edge pattern. In step (b), a plurality of 2-dimensional non-linear interpolation coefficients are obtained based on the edge pattern. In step (c), it is determined whether an edge exists among the plurality of pixels around the pixel to be interpolated. In step (d), data values associated with n*n pixels around the pixel to be interpolated are multiplied by a plurality of vertical and horizontal interpolation coefficients to perform linear interpolation when it is determined that an edge does not exist in step (c). In step (e), data values associated with the plurality of adjacent pixels are multiplied by the plurality of 2-dimensional non-linear interpolation coefficients to perform non-linear interpolation near an edge when it is determined that an edge exists in step (c).